22. Generate Parentheses

 22. Generate Parentheses

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

 

Example 1:

Input: n = 3
Output: ["((()))","(()())","(())()","()(())","()()()"]

Example 2:

Input: n = 1
Output: ["()"]

 

Constraints:

• 1 <= n <= 8

Solution in C++

class Solution {

public:vector<string>ans;

    

    void helper(int o,int c,string &s){

        if(o==0 && c==0){

            ans.push_back(s);

            return;

        }

        if(o>0){

            s.push_back('(');

            helper(o-1,c,s);

            s.pop_back();

        }

        if(c>0){

            if(c>o){

               s.push_back(')');

            helper(o,c-1,s);

            s.pop_back();  

            }

           

        }

    }

    vector<string> generateParenthesis(int n) {

        string s="";

       helper(n,n,s);

        return ans;

    }

};